The control of membrane conductance by acetylcholine receptor at the garter snake neuromuscular junction and by extrajunctional receptors will be studied. Snake myoneural junctions in both twitch and slow fibers are anatomically similar to those in most higher vertebrates including man, and exhibit a host of essentially identical functional properties. Neuromuscular junctions will be located visually using Nomarski optics on twitch fibers and by induced response on slow fibers. The responses of junctional ecetylcholine receptors to various chemical agonists as a junction of temperature voltage and with different permeations will be recorded using the single channel method. In turn, these records will be processed and analyzed using single channel ensemble analysis to obtain information on receptor kinetic properties. Extrajunctional acetylcholine receptors will be studied similarly and their properties compared with those of junctional receptors. A significant portion of our knowledge of acetylcholine receptor mechanisms has been obtained by such studies. This work on the garter snake muscle is designed to continue the characterization of normal receptor mechanisms and to extent these studies to extrasynaptic receptors. Both the permanent population of extrasynaptic receptors near the tendinous insertion on the muscle and denervation induced receptors will be examined. Evaluation of receptor kinetic properties will allow a better understanding of the molecular mechanisms which control membrane conductance changes. This approach should be applicable to other chemical receptors.